A fin is a basic element of a plate-fin heat exchanger. A heat exchange process in the plate-fin heat exchanger is mainly accomplished through heat conduction of the fin and convection heat transfer between the fin and fluids. The fin is a secondary heat exchange surface, not only can expand a heat transfer area and improve compactness and heat transfer efficiency of the heat exchanger, but also can support a core body and improve strength and a pressure bearing capability of the heat exchanger.
As an efficient, compact, and lightweight heat exchange device, the plate-fin heat exchanger has been widely applied to the fields such as the petrochemical industry field, the aerospace field, the electronic field, the metallurgy field, and the machinery field, and achieves remarkable economic benefits in using heat energy, recovering waste heat, saving materials, reducing costs, and some special uses. The plate-fin heat exchanger is one of efficient and compact heat exchange devices, and has the fin between plates as a main heat transfer element. Commonly fin forms used mainly include: a plain fin, a serrated fin, a wavy fin, a louvered fin, a split fin, and the like. A surface characteristic of the fin decides characteristics of fluid flow and heat transfer in the entire heat exchanger. As the gradually expanding of the application range of the plate-fin heat exchanger, higher requirement should be imposed on the fin performance. It is increasingly urgent to need to develop new types of fins.
The coke oven can perform high-temperature carbonization treatment on coal, efficiently convert the coal into products such as coke, coke oven gas, coal tar, and crude benzene. The coke oven is an energy conversion furnace. Among the kinds of coke oven expending heat, the heat brought out by raw coke oven gas with the temperature of 650° C. to 700° C. accounts for approximately 36%, has extremely high recovery and utilization value.
In a device for recovering waste heat of raw coke oven gas in an ascension pipe of a coke oven, heat recovery efficiency can be greatly increased by using a wall type heat exchanger. However, the raw coke oven gas flows from bottom to top inside a drum, and the heat transfer medium also flows in the heat transfer tube which is disposed on the outside of the drum from bottom to top, it presents a parallel flow type between the raw coke oven gas and the heat transfer medium. For a drum wall inside which the raw coke oven gas flowing, because the lower part is affected by the convection heat transfer of the raw coke oven gas and the radiation heat transfer both of the raw coke oven gas and the furnace, the lower part temperature is obviously higher than that of the upper part. Therefore, similarly, a temperature of a lower part of a straight fin is obviously higher than that of an upper part. Moreover, at the same height position, a temperature at the top (far from drum wall) of the straight fin is higher than that of at the bottom (near to drum wall) of the straight fin. If a conventional straight fin of a rectangular thin plate structure was directly welded to the inner drum wall of the raw coke oven gas passage, for the top of each straight fin, the lower part should have a higher thermal expansion rate than that of the upper part, and at the same height position, the top of the fin should have a higher thermal expansion rate than that of the bottom part. Therefore, for an entire straight fin, the expansion might be relatively complex and different everywhere, and the expansion should be inconsistent with that of the drum wall. Eventually, a case in which welding seams between the straight fins and the drum wall should be disengaged due to tearing, resulting in the failure of the heat transfer area of the straight fins.